U.S. patent number 4,494,826 [Application Number 06/108,933] was granted by the patent office on 1985-01-22 for surface deformation image device.
Invention is credited to James L. Smith.
United States Patent |
4,494,826 |
Smith |
January 22, 1985 |
Surface deformation image device
Abstract
A device capable of spatially modulating a collimated read-out
light beam with an input image is described. The most essential
elements of the key unit in this device include a photoconducting
layer, charged grille-structure, an elastomer, and a thin metal
anode. Real-time and storage operation is possible.
Inventors: |
Smith; James L. (Grand Prairie,
TX) |
Family
ID: |
22324892 |
Appl.
No.: |
06/108,933 |
Filed: |
December 31, 1979 |
Current U.S.
Class: |
359/294 |
Current CPC
Class: |
G11C
13/041 (20130101); G02B 26/0825 (20130101) |
Current International
Class: |
G02B
26/00 (20060101); G02F 001/29 () |
Field of
Search: |
;350/360,359 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Sikes; William L.
Assistant Examiner: Scott, Jr.; Leon
Attorney, Agent or Firm: Lane; Anthony T. Gibson; Robert P.
Sims; Robert C.
Government Interests
The invention described herein may be manufactured, used, and
licensed by or for the Government for governmental purposes without
the payment to me of any royalties thereon.
Claims
I claim:
1. A surface deformation image device comprising a plurality of
laminated layers; a first layer being a transparent supporting
substrate; a second layer being a grille structure layer; a third
layer being photoconducting layer in electrical contact with said
grille structure layer; a fourth layer being an elastomer layer; a
thin metal film coating layer on said elastomer layer; terminals
being connected to said thin metal film layer and said grille
structure layer such that electrical potential can be applied
across said layers, excepting said first layer, causing selective
declination of the elastomer layer and therefore the metal film
coating, said elastomer layer relaxing in corresponding areas of
said photoconductive layer which are struck by electromagnetic
energy; an electrical switch; and said grille structure being made
up of a plurality of lines connected to said electrical switch such
that alternate lines are connected to given voltage polarity and
the lines remaining may be switched to either similar or opposite
voltage.
2. A device as set forth in claim 1 wherein said grille structure
layer is inside said photoconductive layer.
3. A device as set forth in claim 1 or 2 wherein said
photoconductor layer is of the type which requires high electric
field for significant photoconduction such as CdS powder in
plastic.
4. A device as set forth in claim 1 wherein a nonconducting light
blocking layer is situated between said photoconductor and said
elastomer layers.
Description
BACKGROUND OF THE INVENTION
Surface deformation image devices fall into three categories.
First, there is the Eidophor-type projector which uses an electron
beam to cause deformation in an oil surface in such a way as to
modulate light being projected through it. Thus, after passing
through Schlieren-type optics, the light is displayed on a screen.
The light pattern is related to the electron beam modulation. In
this way a television program can be projected brightly on a large
screen. Very closely related is the G.E. coherent light value which
is essentially the same except that coherent light is projected
through, and the electron beam modulation may be such as to produce
a hologram pattern, rather than the image itself. Secondly, the
photothermoplastic devices undergo deformation during a heating
cycle according to the electric field pattern across it induced by
light falling on an adjacent electrode-coated photoconductor layer.
The free surface is coated with positive ions generally created
from a nearby corona discharge. A cooling cycle then freezes the
deformation in the surface. Such a device can be used to store
images or holograms. The third category is what Xerox Corporation
calls the Ruticon family of devices. (IEEE Transactions on Electron
Devices, Vol. ED- 19, No. 9, September 1972, pages 1003-1010 and
Applied Optics, Vol. 14, No. 8, August 1975, pages 1770-1771. These
devices can be used for realtime or storage applications. The
advantage of this family is that no television electronics or
heating-cooling cycle is required for their operation. There are
three types of Ruticons, but the one which is most closely related
to the present invention disclosure is the so-called
.gamma.-Ruticon (Gamma Ruticon).
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatic showing of a surface deformation image
device;
FIG. 2 is a diagrammatic showning the grille structure of the
present invention;
FIG. 3 is a showning of the embodiment of the present invention;
and
FIG. 4 is a showning of the embodiment in an overall system.
DESCRIPTION OF THE PREFERRED EMBODIMENT
A drawing of the .gamma.-Ruticon is shown in FIG. 1. (not claimed,
for comparison only.) Light strikes the device from the left. It
passes through spatial modulator 102, a transparent substrate 103,
a negative potential transparent conductor 104, and into a
photoconductor layer 105. This causes a charge redistribution and,
hence, a change of electric field across the following elastomer
layer 106. Since the following metal layer 107 is very thin, the
inhomogeneous field causes deformation of the elastomer and, hence,
the output metal surface. For imaging applications, a spatial
modulation (e.g. a Ronchi ruling) is imposed on the input light.
Thus, a bright portion of the input image induces periodic
deformation on the output surface, and no deformation elsewhere. A
well collimated light source 108 which reflects off the output
surface is no longer collimated where there is light on the input
surface and retains collimation elsewhere. The reflected beam then
passes through a lens 109 with an opaque stop 110 at the focal
point which eliminates collimated reflected light, but not the rest
because it passes around the stop. A following lens 111 then
focuses an output image on a screen 112. The .gamma.-Ruticon can be
used several ways: As an image intensifier, an image wavelength
converter, and, if a negative of the input image is allowable, an
incoherent-to-coherent light converter accomplished by replacing
the opaque stop by a pinhole stop.
Undesirable limitations on the .gamma.-Ruticon are (1) the input
spatial modulator cannot exceed approximately 25 lines/mm without
poor output contrast, i.e. resolution is limited, (2) if storage of
an image is required after its removal, dark current leakage in the
photoconductor limits image retention to approximately 2 minutes,
and (3) when incoherent-to-coherent conversion of image light is
desired, one obtains the negative of the input image.
The invention disclosed here addresses the three undesirable
limitations on the .gamma.-Ruticon. Because of the different
structure concept proposed, a versatility is attained which allows
one to eliminate or reduce one or more of the aforementioned
problems with each design/use option, which consists mainly of
scaling and operating procedure. The structure difference consists
first of placing a charged grille structure in (or in contact with)
the photoconductor, letting the applied bias exist between the
grille and the fixed-potential metal layer on the output surface.
The discontinuous nature of the grille structure (FIG. 2)
eliminates the need for a spatial modulator on the input light and
makes possible a second structural difference: The transparent
electrode which the .gamma.-Ruticon has may be entirely eliminated,
Whereas the .gamma.-Ruticon elastomer is normally smooth with zero
input, the disclosed device is normally wrinkled and smooths with
an input.
The invention disclosed here has use in (1) real-time image
intensification for observation of weakly lighted objects, (2)
conversion of image light wavelength, (3) incoherent-to-coherent
image light conversion, and (4) storage of transient images.
Applications to missile systems and aerial reconnaissance are
evident since target or geography recognition and analysis through
optical data processing (which generally needs
incoherent-to-coherent conversion) is highly desirable.
The option to have opposite polarity on alternate grille lines and
a high-resistance photoconductor optimizes storage. A second option
to have all grille lines with the same polarity and a
lower-resistance photoconductor optimizes resolution and speed,
respectively.
The key modulator element is shown in profile in FIG. 3. The
transparent substrate 51 allows light from the left to pass
through. Next, bonded onto the substrate is the grille structure
52, every other line being connected to the same potential and the
remaining connected to the opposite potential. However, a switch 57
provides the option for all grille lines to have the same
potential. Either way, grille lines provide a periodic electric
field in the device. A photoconducting layer 53 is located in front
of and/or between grille lines. This layer is of e.g., uniform Si
or CdS or CdS powder in plastic or gelatin binder, or
polyvinylcarbazole. The next layer 54 is optional; an optical
isolation layer 54 which prevents readout light from striking the
photoconductor. The elastomer 55 follows. A special clear Silicon
rubber is an example of a workable elastomer. The surface of the
elastomer is metallized with a thin, smooth In and/or Au film 56
which is held at a given potential. When an image is focused on the
input side of the modulator, readout light striking and reflecting
off the readout side carries the image which can be observed on a
screen by passing the readout beam through appropriate optics.
OPERATION: GENERAL APPLICATION CONFIGURATION
Referring to FIG. 4, the input light 61 incident on the left
embodies an image which passes through the transparent substrate
and focuses on the photoconducting layer. Readout light 62 incident
from the right (generally collimated, though not necessarily),
reflects off the metallized elastomer in a widely scattered manner
except where incident light has caused the normally wrinkled
metallized elastomer surface to smooth 63. Reflection from the
smooth areas passes through a lens 64, and then a pinhole aperture
65. Most scattered light will not pass through the pinhole whereas
the light reflecting from the smooth regions will pass through (if
readout light is collimated, reflection from smooth regions will
also be collimated and will later pass through a pinhole 65 located
at the focal point of the lens 64.)
After passing through the pinhole, the light encounters another
lens 65 which focuses the transferred image onto a screen 67.
Spatial filtering is possible at the pinhole region, if
desired.
OPERATION: FIRST OPTION REAL-TIME (Refer to FIGS. 3 and 4)
1. Alternate grille lines 52 are of opposite polarity, the metal
film 56 on the elastomer 55 surface is positively (or negatively)
charged. Elastomer-metal surface is wrinkled with the periodicity
of the grille line pairs.
2. Read-in light from the left strikes the device and penetrates to
the photoconducting layer 53. Photocurrent relaxes periodicity in
the electric field due to charge redistribution which shields the
grille lines. Grille lines have high contact resistance with the
photoconductor so that space charge can build up.
3. Negative (or positive) potential on alternate grille lines is
reduced somewhat to aid elimination of electric field periodicity
in the light-exposed region.
4. The elastomer 55 relaxes in the light-exposed region due to the
reduction of electric field periodicity. The metallized surface 56
becomes smooth and specularly reflecting.
5. Read-out light 62 from the right now strikes the metallized
elastomer. Reflected light scatters through wide angles in the
region where the elastomer is wrinkled, but reflects specularly
where the elastomer is smooth. This is the basis for the image
transfer.
6. Read-in light is shuttered off by shutter 68, read-out light is
shuttered off by shutter 69 from the observation screen, and an
erase flash 70 from the left floods the photoconducting layer as
the alternate electric potential on the grid lines is momentarily
reversed. This is the erase (or reset) phase.
7. The grid line potential alternation is changed back to its
original configuration, and the read-in light is introduced from
the left. The cycle begins again.
OPERATION: STORAGE
Use of a nonlinear high-resistivity photoconductor of a type which
requires a high electric field for conduction (e.g.,
photon-assisted barrier tunneling) is appropriate to long-term
image storage. Opposite polarity on alternate grille lines provides
high fields for photoconduction without unnecessarily high,
potentially damaging fields across the elastomer. For storage the
read-in phase and the readout phase are the same as above. Instead
of following with the erase phase, however, the read-in light is
shut off, potential difference between grille lines is reduced, and
the readout light is maintained (or is turned on later when it is
desired to read the last recorded image).
OPERATION: SECOND OPTION REAL-TIME (See FIG. 3)
For applications where speed is important and very short-term
storage is adequate, a conventional photoconductor not requiring
very high fields for charge transport may be used. In this case,
alternate grille lines may be of the same polarity (opposite that
of the output surface electrode) so that resolution (in lines/mm)
is doubled. Switch 57 provides this option.
* * * * *